I have a Juki on a pennywinkle and had the same problem I to had to loosen the quilt top and use 16 or 18 needle. I talked to Sue Patton she is a longarm quilter who teaches longarm quilting and she said it didn't matter what batting you use or thread although cotton does break a little more then and others. Then you have to slow down you must give the needle time to get in the quilt and come back up especially when doing curves....